Toll switching telephone system



J. WICKS TOLL SWITCHING TELEPHONE SYSTEM May l1, 1954 16 Sheets-Sheet 1 Filed Feb. 21. 1952.

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FALSE SEIZE INVEN TOR.

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a; TOLL swITcHING TELEPHONE SYSTEM Filed Feb. 21, 1952 1e sheets-sheet 6- SEQUENCE PAD' CUT-OUT CENTRAL OFF/CE /O REPETER 400 PULSE CUT- /N NTER- PULSE TIMER R630 663 TONE U/v/T l Aflys.

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TOLL SWITCHING TELEPHONE SYSTEM Filed Feb. 21, 1952. l 16 Sheets-Sheet 9 REPEATER 700 RL SE. PULSE TIMER INVEN TOR.

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Filed Feb. 2l. 1952 May 11, 1954 J. WICKS TOLL SWITCHING TELEPHONE SYSTEM Filved Feb. 21. 1952 ,16 Sheets-Sheet 12 QN ESE T0 OTHER TRUNK GIR'S.

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J. WICKS TOLL SWITCHING TELEPHONE SYSTEM May 1l,` 1954 16 Sheets-Sheet l5 Filed Feb. 21. 1952 l INVENToR. John Wicks May 11, 1954 J. wxcKs TOLL swITcHING TELEPHONE SYSTEM 16 Sheets-Sheet 14 Filed Feb. 2l. 1952 May 1l, 1954 J. wlcKs 2,678,355

Tou. SWITCHING TELEPHONE SYSTEM Filed Feb. 21, 1952 v /16 sheets-sheet' 15 BUSY C. 0.

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John Wicks Patented May 11, 1954 TOLL SWITCHING TELEPHONE SYSTEM John Wicks, Biloxi, Miss., assigner to Automatic Electric Laboratories, Inc., Chicago, Ill., a corporation of Delaware Application February 21, 1952, Serial No. 272,741

31 Claims.

The present invention relates to telephone systems and more particularly to toll switching systems involving tandem related offices and exchanges.

In setting-up toll connections in a toll switching telephone system from a first operator switchboard in an originating office to a second operator switchboard in a terminating ofce through automatic switching apparatus in a tandem related exchange, the situation is frequently encountered that while there are an adequate number of toll lines extending betweenthe originating office and the tandem exchange and an adecuate number of trunk lines extending between the terminating oce and the tandem exchange, the automatic switching apparatus in the tandem exchange encounters an all-trunks-busy condition of the trunk lines extending between the tandem exchange and the terminating cnice so that some of the toll connections cannot be immediateiy completed by the operators at the first switchboard in the originating onice. Thus it becomes necessary for the operators at the rst switchboard to make recall slips on these uncompleted toll calls and subsequently to attempt the completion thereof, whereby the operators may be required to maire several attempts before completing any one of these toll calls. This situation is further aggravated in a telephone system where the originating office is a large oiiice and the iirst switchboard comprises a large number of positions and the terminating oiiice is a small cnice and the second switchboard comprises a small number of operator positions, and wherein the normal toll trailic between the tandem exchange and the terminating oince does not warrant the provision of additional trunk lines therebetween.

Accordingly it is the general object of the present invention to provide in the tandem exchange of a telephone system of the character noted, automatic toll call storage and switching apparatus that is rendered operative in response to an all-trunks-busy condition of all of the trunk lines extending between the tandem exchange and the terminating ofiice, and that may then be set by the operator at any operatorposition at the rst switchboard subsequently andautomatically to complete a toll connection on a point-topoint basis from the tandem exchange tothe second switchboard and from the tandem exchange to the first switchboard. l

Another object oi the invention is to provide automatic toll call storage and switching apparatus of the character noted, that is capable of storing a plurality of toll calls and that is subsequently operative successively to set-up the corresponding point-to-.point calls from the tandem exchange to the two switchboards as the trunkA lines extending between the tandem exchange and the terminating oiice become idle, wherein the point-to-point calls are set-up in the same order that the corresponding toll calls are placed in storage.

Another object of the invention is to provide automatic toll call storage and switching apparatus oi the character noted, that is rendered. operative when all of the trunk lines between the tandem exchange and the terminating office become busy and that is then automatically taken into use upon the extension of the next toll call from the nrst switchboard to the tandem exchangewhich requires completion to the second switchboard, and that is selectively held and released under the control oi the calling operator at the rst switchboard after it isV taken into use, whereby the calling operator at the iirst switchboard may handle the particular toll call being extended either on a point-to-point basis or upon a recall basis.

A further object of the invention is to provide in a toil switching telephone system, an automatic toll cali storage and switching apparatus that is operative in conjunction with toll lines that are terminated at the opposite ends thereof in repeaters of the voice-frequency dailing and signalling type.

A still further object of the invention is to provde in a telephone system, improved call storage and automatic switchingV apparatus permitting iiexibility in the manner ci setting-up calls involving a tandem exchange and depending upon the idle or busy conditions oi the trunk groups outgoing from the tandem exchange.

Further features of the invention pertain to the particular arrangement of the circuit elements of the telephone system, whereby the above-outlined and additional operating features thereof are attained. f

Sect. 1..-The general arrangement of the telephone system The invention, both as to its organization and method of operation, together with further cbjects and advantages thereof, will best be understood by reference to the following speciiication taken in connection with the accompanying drawings, in which Figure l is a schematic diagram oi the area served by a telephone system embodying the present invention. and illustratingxthe general arrangement of vthe apparatus incorporated in two offices and one exchange thereof; Figs. 2 to 16, inclusive, taken together, illustrate the dee tails of certain of the apparatus incorporated in one of the oflices and the exchange included in the telephone system, which apparatus has incorporated therein the features of the invention as briefly outlined above; and Fig. 1'? illustrates the mode of combining Figs. 2 to i6, inclusive, to form a unified diagram.

More particularly, Fig. 2 illustrates the details of one of the toll dial circuits incorporated in the central ofiice; Fig. 3 illustrates the details of one of the toll trunk circuits incorporated in the central office; Figs. 4 to 6, inclusive, illustrate the details of one of the repeaters incorporated in the central cnice; Figs. 7 to 9, inn elusive, illustrate the details of one of the repeaters incorporated in the tandem exchange; Fig. 10 illustrates the details of one of the iinder links incorporated in the tandem exchange; Fig. 11 illustrates the details of one of the toll selectors incorporated in the tandem exchange; Fig. 12 illustrates the details of the call storage circuit incorporated in the tandem exchange; Figs. 13 and114 illustrate the details of one of the busy set-up circuits incorporated in the tandem exn change; and Figs. 15 and 16 illustrate the details of the sender individually associated with the busy set-up circuit mentioned and incorporated in the tandem exchange.

Referring now more particularly to Fig. l, the telephone system there illustrated serves an area including a central office lil, a tandem exchange 2U, a remote oiiice 3i) and certain other exchanges associated with the tandem exchange 2@ and not illustrated. The central ofce iii and the tandem exchange 2G are of the automatic type; while the remote oice Si) may be of any suitabie type, either manual or automatic. The central office III and the remote oiiice 3G comprise primary toll centers; while the tandem exchange 2t occa1 pies a tandem position in the area with respect to the central oice lll and the remote office The central ofiice lli comprises a toll board ttt that may be of any suitable manual dial type,

such, for example, as a Western Electric Cornpany No. 3; and, likewise, the remote office 3i) comprises a toll board i'i that may be of any suitable manual dial type, such, for example, a Western Electric Company No. 3. The central office IB serves a number of subscriber suhsta tions, including the subscriber substation Ti; the tandem exchange 2@ serves a number of subscriber substations, including the subscriber substation T2; and the remote office 3d serves a number of subscriber substations, not shown.

Preferably, the automatic switching apparatus incorporated in the central office it is of the Strowger type, including a local switch train, not shown, for the purpose of setting up local calls therein, and a toll switch train for setting up toll calls; and, preferably, the automatic switching apparatus incorporated in the tandem exchange 2B is of the Strowger type including a local switch train, not shown, for the purpose of setting up local calls therein, and a toll switch train for setting up toll calls. The central ofnce I0 and the tandem exchange 2li are intercon nected by a fairly large group of trunk lines, including the trunk line 102; and the tandem exchange and the remote oihce 30 are interconnected by a fairly small group of trunk lines, including the trunk line 125i. As illustrated, the group of trunk lines interconnecting the central onice I0 and the tandem office 20 comprises ten individual trunk lines; while the group of trunk lines interconnecting the tandem exchange 20 and the remote ofiice t@ comprises three individual trunk lines. Each of the trunk lines 102, etc., may include one or more voice current repeaters 103, etc., since these trunk lines are fairly long; while each of the trunk lines 125|, etc., may be of the straight metallic type, since these trunk lines are fairly short. Each of the trunk lines 102, etc., terminates at the opposite ends thereof in Asubstantially identical repeatersrespectively disposed in the central oiiice i0 and in the tandem exchange 2li, the trunk line 702iy respectively terminating in the repeaters 400 and respectively disposed in the central office i0' and in the tandem exchange 20. Each of the trunk lines itl, etc., terminates at the opposite ends thereof in a trunk circuit disposed in the tandem exchange 2t and in a ring-down trunk circuit disposed in the remote office 30, the trunk line i255 terminating in the trunk circuit disposed in the tandem exchange 20 and in the ring-down trunk circuit i230 disposed in the remote ofce Sli. Each of the repeaters 409, etc., is provided with an individually connected tone unit Eel, etc., and an individually connected incoming toll selector ttt, etc., in the central office It; while each of the repeaters 1w, etc., isprovided with an individually connected tone unit 70H, etc., and an dividually connected incoming toll selector iilt, etc., in the tandem exchange 2S.

ln the central oiice l0, each operator position at the toll board 393 has access to an individual group of toll dial circuits via an individual group of outgoing trunks, the first operator position having access to the group of toll dial circuits 2&6, etc., via the individual group of outgoing trunks 2M, etc. Likewise, at the toil board 55E-i, each operator position is accessible to an individual group of toll trunk circuits via an individual group of incoming trunks, the first cperator position being accessible to the individual group of toll trunk circuits 369, etc., via the individual group of incoming trunks Sti, etc. Each of the toll dial circuits 2M, etc., is connected to a toll selector 203, etc., individual thereto, the toll selectors 263, etc., having access to the repeaters fitti, etc. Specifically, the toll selector 2633 has access to the outgoing trunk @ist extending to the repeater ddii; the repeater et@ being connected via the incoming trunk ddii to the incoming toll selector 3G23 as previously noted. The incoming toll selectors tilt, etc., have access to the toll trunk circuits 3M, etc., via the incoming trunk 302, etc., extending thereto. Also, the incoming.l tollselectors 333, etc., have access to a toll switchtrain, indicated generally at Stil, via incoming trunks 307i, etc; while the toll switch train 3M has access to the subscriber lines extendingv to the subscriber substation Tl, etc., in the central ofce ill. For example, the toll switch train tdhasaccess to the subscriber line 305 extending to the subscriber substation Ti and provided with the individual line circuit 395. In the central office l@ the toll selectors 203, etc., the incoming toll selectors ses, etc., and the toll switch train 30-'5 comprise component elements of the toll. switching apparatus.

In the remote officev each operati-ir position at the toll board i216. has access to the ringdown trunk circuits i, etc., via outgoing trunksl25i, etc., and is accessible to the ringdown trunk circuits i260, etc., Via incoming trunks, i262, etc.

n the tandem exchange 20 the trunk circuits |250, etc., are provided with individually connected incoming toll selectors |253, etc., via incoming trunks |252, etc. Also the trunk circuits |250, etc., are accessible to a call storage circuit |250 via individual outgoing trunks |201, etc. The incoming toll selectors |253, etc., have access tothe repeater 100, etc., via outgoing trunks 566, etc.; and the incoming toll selectors |608, etc., have access to a group of toll selectors, including the toll selector |00, that, in turn, has access to the call storage circuit |200. For example, the incoming toll selector |008 connected to the repeater 100 via theincoming trunk 005 has access to the toll selector via the incoming trunk HEI. Also the incoming toll selectors |253, etc., and the incoming toll selectors |008, etc., have access to a toll switch train |255 via incoming trunks |254,etc.; while the toll switch train |255 has access to the subscriber lines extending to the subscriber substation T2, etc., in the tandem exchange 20. For example, the toll Vswitch train |255 has access to the subscriber line |255 extending to the subscriber substation T2 and provided with the individual line circuit |251. In the tandem exchange 20' the incoming toll selectors |253, etc., |008, etc., the toll selec tors |00; etc., and the toll switch train |255 comprises coinponent elements of the toll switching apparatus.

Also, the tandem exchange 20 comprises a small group of finder links, including the finder link |050, and an associated distributor H03. The distributor |03 is commonly associated with the finder links |000, etc., and is provided with a start network commonly associated with the toll selectors H00, etc. Also, the tandem exchange 25 comprises a small group of busy set-up circuits 1355, etc., each provided with individually associated senders |500, etc., and individually associated registers |50|, etc. Each ofthe finder links |050, etc., comprises three individual nder switches having respective access to the group of toll selectors H00, etc., to the group of repeaters 100, etc., and to the group of busy set-up circuits |350, etc. For example, the iinder link |000 comprises the first finder switch Fl having access to the outgoing trunk H02 extending to the toll selector |00, the second nder switch F2 having access to the outgoing trunk 905 extending to the repeater 100, and the third iinder switch F3 having access to the trunk |40| extending to the busy set-up circuit |300.

Sect. 2.-The apparatus incorporated in the telephone system In the central ofce |0 the toll board 303 may be of the manual dial type Western Electric Company No. 8, as previouslylnoted; theline circuits 366, etc., may be of any suitable type; the toll selectors 203, etc., may be of the Strowger type; the incoming toll selectors 308, etc., may be of the Strowger type; and the toll switch train 304 may be of the Strowger type.

The toll dial circuits 200, etc., are identical; the toll dial circuit 200 comprising, :as shown in Fig, 2, a relay group including a busy relay R2|0, a sleeve relay R225, a dial start relay R230, a ready relay R240, a switch-through relay R250, a prepare relay R260, la supervisory relay R210, a switch relay R280 and anV end dial relay R250.

The toll trunk circuits'300, etc., are identical; the toll trunk circuit 300 comprising, as shown in Fig. 3,- a relay groupincluding two transfer relays R310 and R320, a controlfrelay R325', a

ring relay R330, a prepare relay R340, a re-ring relay R350, a sleeve relay R360, a re-ring relay R310 and a seize relay R380.

The repeaters 400, etc., are identical; and preferably these repeaters are substantially identical to the repeater disclosed in Figs. 4to 6, inclusive, of U. S. Patent No. 2,517,515, granted on August 1, 1950, to John Wicks and Otho D. Grandstaff.` Specifically, the repeater 400 comprises, as shown in Figs. 4 to 6, inclusive, a relay group including a series relay R4H), a release relay R420, a line relay R430, two release pulse timer relays R535 andR440, a selector seize relay R056, an incoming release relay R450, a tandem test relay R410, a line supervisory relay R460, an answer supervisory relay R490, a re-ring relay R400, an answerl supervisory relay R5I0, a supervisory control relay R520", va supervisory rel-ay R530, a ring relay R535, threering control relays R550, R550 and R560, a switch-over relay R510, a dial-in relay R500, a control relay R590, a loop test relay R500, a control relay R505, three wait relays X500, Y506 and Z500, a supervisory relay vRiil), a signal-in relay R620, an interpulse timer relay R530, a switch-through relay R540, a guard relay R550, a supervisory pulse relay R665, a prepare relay R610, a send relay R615, a sequence relay R600,'a pad control relay R650 and a pad cut-out relay R660, as well as a toll pad 665. Specifically, the Vconnection and arrangement of the relay group in the repeater 460 diier from that incorporated in the repeater disclosed in Figs. a to 6, inclusive, of the previously mentioned Wicks and Grandsta patent in the inclusion of the three wait relays X500, Y560 and Z500 that are employed for a purpose more fully explained hereinafter.

The tone units 60|, etc., are identical; and the tone unit 60| is connected and arranged in the lmanner of the tone unitdisclosed in U. S. Patent No. 2,482,478, granted on September 20, 1949, to Otho D. Grandstai. For example, the tone unit 60|, indicated in Fig. 6, comprises both a senderV and a receiver of unmodulated audio frequency signals and iixed frequency modulated audiofrequency carrier signals. Specifically, the tone unit 60| is adapted to send and to receive unmodulated 1000 cycle audio frequency signals, as well as to send and to receive 60 cycle modulated 1000 cycle audio frequency carrier signals; which signals are utilized for the purpose of digit control, seizure control, supervisory control and release control, as explained more fully hereinafter. Also, the tone unit 60| comprises a relay group, not shown, including modulation cut-off relay, a re ceive switch relay, a pulse cut-in relay, an impulse-in relay and a signal-in relay; as well as a group of conductors extending to the associated repeater 400 and including a sending-conductor C60|,a sending '-1- conductor C602, a monitoring -Vconductor C603, a monitoring conductor C604, a receiving conductor C605, a Yreceiving conductor C606, a receiving switch conductor 7. circuits |250, etc., may be of any suitable type.

The repeaters 700, etc., are identical; and preferably these repeaters are substantially identical to the repeaters disclosed in Figs. 4 to 6, inclusive, of the previously'mentioned patent of John Wicks and Otho D. Grandstaif. Specifically, the repeater. 100 comprises, as shown in Figs. 7 to 9, inclusive, a relay group including a series relay R9 i 0, a release relay R920a line relay Rte, two release pulse timer relays R930 and R040, a selector seize relay R950an incoming release relay R900, a tandem test relay Reli), a line supervisory relay R980, an answer supervisory relay Regi), a re-ring relay R900, an answer supervisory relay REIS, a supervisory control relay Rile, a supervisory relay R330, a ring relay R835, three ring control relays REMO, R856 and Rt, a switch-over relay Rl'l, a dial-in relay R830, a control relay R890, a loop test relay R800, a control relay. R305, three wait relays X300, Yiil and Z300, a supervisory relay Rl l0, a signalu in relay R720, an interpulse timer relay R130, a switch-through relay R740, a guard relay R750, a supervisory pulse relay R760, a prepare relay R', a send relay RWS, a sequence relay R188, a pad control relay R190 and a pad cut-out relay R'l00, as well as aftoll pad lil. Specifically, the connection and arrangement of the relay group in the repeater '|00 differ from that in corporated in the repeater disclosed in Figs. 4 to 6, inclusive, of the previously mentioned patent of Wicks and Grandstaff in the inclusion of the three wait relays X800, Yl and Z801! that are employed for a purpose more fully explained hereinafter.

The tone unitslili, etc., are identical; and the tone unit '|05 is connected and arranged in the manner of the tone-unit disclosed in the previ ously mentioned patent of Otho D. Grandstai.

For example, the'tone unit 16|, indicated in Fig. 7, comprises both a sender and a receiver of unmodulated audio frequency signals and fixed frequency modulatedk audio frequency carrier signals. Specically, the tone unit l! is adapted to send and to receive unmodulated 1G00 cycle audio frequencysignals, as weil as to send and to receive 60 cycle modulated 10150 cycle audio frequency carrier signals; which signals are utilized for the purpose of digit control, seizure control, supervisory control and release control, as explained more fully hereinafter. Also,-the tone unit 'isi comprises a relaygroup, not shown, including a modulation cut-ofi relay, a receive switch relay, a pulse cut-in relay, an impulse-in relay and a signalun relay; as well as a group of `conductors vextending to the associated repea-ter sd and including a sending conductor Citi, a sending conductor C102, a monitoring conductor Ci, a monitoring conductor C704, a receiving conductor C505, a receiving -lconductor Citt, a receiving switch conductor C210?, a modulation cut-oit conductor C700, asignal-in conductor C'ifl, a dial-in conductor C'lil and a pulse cut-in conductor Cl'l i. Finally, the tone unit lul comprises a 60 cycle generator. and a 1000 cycle generator, as well as alvacuum tube relay circuit, not shown.

The finder links |000, etc., are identioal;. and the iinder link i000 comprisesas shown inFig. .10, the three individual iindei'svvitches El, F2 and F3, as previously noted. The finder. switch Fi is of the rotary type including` eightindividual wipers provided with contact banks; terminating the. individual conductors4 in the trunks'v H02; etc., extending to thetollselectors. ll|00, etc., as

Well as a rotary magnet EM for driving the wipers noted step by step in the clockwise direction. The finder switch F2 is of the rotary type including four individual wipers provided with contact banks terminating the individual conductors in the trunks mit, etc., extending to the repeaters lil, etc., as well as a rotary magnet 2M for driving the wipers noted step by step in the clockwise direction. The nder switch F3 is of the rotary type including eight individual wipers provided with contact banks terminating the individual conductors in the trunks |40|, etc., ex tending to the busy set-up circuits |3i0, etc., as well as a rotary magnet 3M for driving the wipers noted step by step in the clockwise drection. Also, the iinder link Hitt comprises a relay group including a switch relay Riiii, a start relay Ri02t, a stop send relay R|025, an end dial relay |030, two control relays Riis and Rifii, two count relays Ri and R'at, a ring relay RI 055, a release relay Ri 05u, a switch relay Rl tit, a re-ring relay Riliil, a test relay Rlilt' and a switch relay Riitl;

The toll selectors illl, etc., are identical; and the toll selector litt comprises, as shown in Fig. l1, a Strowger mechanism i |86 including a wiper carriage carrying four wipers, a vertical magnet Mi ii for driving the wiper carriage step by step in the vertical direction away from its normal vertical position, a rotary magnet Ml E83 for driving the wiper carriage step by step in the rotary direction away from its normal rotary position, and a release magnet MMSE for releasing the wiper carriage and for causing it to be returned to its normal rotary and ver 'cal positions.

The Strowger mechanism H83 also comprises a contact sank associated with the wiper set and terminating the trunks extending to the various destinations including the trunks extending to the call waiting circuit ldt. Further, the Strowger mechanism litt comprises a vertical control wiper VvV carried by the wiper carriage and associated with a vertical control contact bank that is employed for a control purpose more fully explained hereinafter. Associated with the Strowger mechanism H are two sets of switch springs Sl and SI 87 that are operated when the wiper carriage is moved in the vertical direction one step away from its normal vertical. position, a set of switch springs SI |89 that is operated when the wiper carriage moved in the vertical direction a predetermined number of steps corresponding to a given levei of a number of adjacent levels in the associated contact bank terminating trunks extending to a destination, not shown, as well as a set of switch springs Si |88 that is operated when the wiper carriage is moved in the rotary direction eleven steps away from its normal rotary position.

Further, the toll selector ltil comp-rises a relay group, including a test relay Rl I l0, a distributor start relay Ri 20, a wait relay Ri |25, a switch relay RiiSii, a line relay Rl |40, two hold relays R||4l` and Rilll, a busy relay RUSS, a pulse delay relay RHEG, a control relay Rli, a step relay RI il!! and a change-over relay Rl H5.

The call storage circuit |200 comprises, as shown in Fig. 12, first, second and third trunks |20I, |202 and |203 respectively extending to the three trunk circuit |250, etc., respectively terminating the three trunk lines I25|, etc., extending between the tandem exchange 20 and the remote office 30'. Also, the call storage circuit comprises first, second and third call storage trunks |204, |205 and |206, as Well as four other 

